1. Field
Exemplary embodiments relate to a robot. More particularly, exemplary embodiments relate to a robot including an actuator having an improved structure to drive finger joints.
2. Description of the Related Art
The use range of a robot has been gradually enlarged over all industrial fields. In particular, studies and research on a human-type robot have been accelerated. Accordingly, in order to conduct housework instead of a human being, the human-type robot must safely and quickly grasp and manipulate a variety of objects.
Since the human-type robot has a restricted hand size, several large-scale motors cannot be installed in robot hands. Accordingly, since the capacity of a motor used for the robot hand is small, the grasping force of the robot hand is less than that of the hand of the human being. In addition, since the robot hand is structurally restricted, the robot hand has a degree of freedom less than that of the hand of the human being.
In order to increase the grasping force of the robot hand, it may be considered that a large-scale motor (generating large force) is installed in a robot arm (forearm part) instead of the robot hand, and wires transmit driving force of the motor to a finger joint. In this case, the wires pass through a wrist joint linking the robot hand with the forearm, and are wound around two pulleys in order to reduce friction caused when the wires pass through the wrist joint.
However, if the wrist joint operates, the two pulleys move, and an actuator moves in a yaw direction. The length of the wire is changed due to the movement of the actuator in the yaw direction. Since the length of the wire is restricted, the finger joint operates by the wire in order to cope with the length change of the wire. Accordingly, in order to prevent the operation of the wrist joint from exerting an influence on the movement of the finger joint, the operation of the finger joint must be individually controlled when the wrist joint operates. Such a driving structure complicates controlling of the finger joint due to the movement of the wrist joint.
Accordingly, it is necessary to consider a structure in which the length of the wire is not changed even if the wrist joint operates. In other words, the wire passes through the wrist joint coupling the forearm part with the robot hand, and is inserted into a tube, so that the length of the wire is constantly maintained even if the wrist joint operates. In this case, the tube constantly maintains the length of the wire regardless of the operation of the wrist joint. Therefore, even if the wrist joint operates, since the length of the wire is not changed, it is unnecessary to additionally control the actuator driving the wire.
However, the tube, into which the wire is inserted, causes friction with the wire. Accordingly, the driving force of the actuator is significantly lowered due to friction between the wire and the tube, and this is increased as range of motion of the wrist joint is increased. If the range of the motion of the wrist joint is increased, the tube is excessively bent, so that the friction between the wire and the tube is increased. Accordingly, in such a driving structure, power transmission efficiency of the actuator is remarkably reduced, and the range of the motion of the wrist joint is restricted.